By formally designating Syria a civil war, the International Committee of the Red Cross may have inadvertently revealed an uncomfortable prospect for the country’s future: Civil wars are typically protracted and bloody as both sides fight with their backs to the proverbial wall. And they rarely result in the complete vanquishing of either combatant party; far more common are political and territorial compromises that redefine the state. But when a civil war fought on sectarian religious lines reaches the capital city and the seat of power — as it did last weekend, prompting days of continuous fighting involving armor and artillery that continued to rattle Damascus into Wednesday morning, with Syria’s state-run TV saying that the country’s defense minister was killed in a suicide blast — the prospects for any kind of soft landing via a political settlement may have been eclipsed, leaving the country’s fate in the hands of its hard men.

Rebel propagandists touted their military operation in the capital as the beginning of a final offensive, but its scale suggested a more limited but nonetheless decisive objective: By forcing the regime to use armor and artillery in the capital, the rebels have sent a message to the regime’s key support bases that Assad has lost control of much of the country and that his promises to crush the rebellion ring hollow. The blast at national security headquarters that killed defense minister Daoud Rajiha and also deputy army chief, Assef Shawkat — who is also President Bashar Assad’s brother-in-law — is a signal that the regime’s ability to protect even its inner core is crumbling.

“It happened in the most guarded neighborhood inside Damascus, very close to where Bashar and his mother and other family members are, and where there are many intelligence locations,” retired Syrian Brigadier General Akil Hashem, who is in exile in Paris, told TIME. “I received information that a bodyguard in the inner sanctum of the regime was the one who placed the explosives inside the building, and now Syrian television is confirming that too. The regime is collapsing from inside.”

The latest violence in Damascus may not spell the imminent collapse of the Assad order, but it puts the regime’s fate in writing on the wall: “Once the fighting gets into the key cities, the advantage passes from the military to the insurgents,” says Joshua Landis, a Syria expert at the University of Oklahoma. “As long as the fighting is confined to villages and small towns, those can be surrounded and pounded into submission with artillery fire. You can’t do that in a city of 5 million people. Your heavy weapons become meaningless, because you can’t destroy Damascus — and so, the city’s Sunni neighborhoods become a sea in which the rebels can swim and multiply.”

By some accounts, the military during the past three days ordered whole neighborhoods in the capital to evacuate their homes in order to clear the rebels from Sunni areas. Not only do such actions confirm to the citizenry that the regime faces a popular insurrection rather than simply a terrorism problem, as its propagandists claim; they also build resentment against the security forces and create an even more permissive environment for the insurgents. “But if the regime can’t drive the rebels out of the capital,” Landis notes, “the regime is finished.”

The brutality and mounting chaos of a war that has already claimed some 16,000 victims has certainly prompted many of the regime’s key Sunni backers to reconsider their allegiance. Assad’s regime is founded and maintained on an inner core of Alawites, a community which sees its interests and fate intimately tied to that of the ruling family and views the rebellion as a mortal threat. But the Alawites are just 12% of the population, and the regime has also relied on the backing of Syria’s Christians (some 10%), Druze (3%), and other minorities, as well as political and business elites from among the Sunni majority to be able to govern the sprawling country. Eighteen months into the rebellion, the regime may no longer be able to count on its Sunni backers. And without them, it cannot for long maintain its rule over all of Syria.

Two high-profile defections earlier this month — top military man Gen. Manaf Tlass and former Ambassador to Iraq, Nawaf al-Fares — prompted many headlines suggested the regime was nearing collapse. But the unfortunate reality of Syrian power politics is that the significance of their defections has to be read through a sectarian prism. Both men were amongst the most senior Sunni figures of the regime, as have been all 13 generals that have jumped ship thus far. So far, there has been no sign of elements of the regime’s Alawite core being willing to jump ship. So the regime is certainly weakening, and its ability to govern all of Syria and restore the old order may be fatally damaged. But that doesn’t necessarily portend its imminent collapse.

“Until now, not a single Alawite, Christian or Druze of any significance within the military-political complex is known to have left Assad’s side,” notes Aron Lund, an analyst at Sweden’s Olaf Palme Center. “The fact that this core of religious minorities has remained cohesive is one explanation for the regime’s relatively strong position after more than a year of popular rebellion. It is also the reason that it can’t extinguish the uprising – Assad lacks both the manpower and the moral authority among Syria’s 65% Sunni-majority population. This growing sectarian polarization is now putting severe strain on the long-running alliance between Alawite and rural Sunni military families (as well as on the parallel alliance between the military and the Sunni urban commercial bourgeoisie).”

But, warns Lund, the loss of its Sunni allies won’t be enough to bring down the regime.

“Large-scale Sunni disavowal of the regime would in itself not be enough to convince most of the Alawite hard core around the president that the battle is lost,” he writes. “Quite the contrary, these members of the ‘inner regime’, who lack a safe exit from the conflict, are likely to try to dig down further in their home areas in northwestern/northeastern Damascus and western Syria, regardless of the fate of the rest of the country.”

It’s beyond doubt, now, that the decades-old political order of Alawite minority rule over all of the former Ottoman province on which modern Syria emerged at the end of World War I is nearing its denouement. The fight, now, may be increasingly over how and by what it is replaced. Despite a common sense of the dangers arising from the collapse of the Syrian state, divergent geopolitical stakes in the Middle East leave the international community unable to forge a joint response. Western and Arab powers are pressing for President Bashar Assad’s ouster, while Russia, China and Iran looking to prevent regime-change. U.N. Special Envoy was in Moscow Tuesday, hoping to convince Russia to put more pressure on Assad ahead of a Security Council vote on the future of its observer mission, while Secretary General Ban Ki Moon is doing the same in Beijing. But Western powers are unlikely get Russian and Chinese support for a new resolution threatening sanctions against the regime if it fails to pull back its forces.

Western powers remain reluctant to consider unilateral military intervention in Syria, mindful not only of their limited resources and political capital in the Middle East, but also of the perils inherent of taking effective ownership of a country in the throes of a civil war with region-wide consequences. At the same time, reports last week that U.S. officials believe the Assad regime has recently moved some of its known chemical-weapons stocks have underscored some of the dangers inherent in the regime’s collapse. While opposition figures insist Assad might use such weapons to ensure his regime’s survival, many Western analysts believe the regime may simply be safeguarding a key strategic asset against the prospect of international intervention or rebel territorial gains. Either way, that concern is a reminder of the potentially devastating consequences of Syria’s collapse.

But absent any prospect for a political solution between a regime digging in for a fight to the finish and an opposition that remains incorrigibly divided even as military rebels become more organized and capable — and determined to bring down Assad at any cost — Syria’s future looks set to be decided with arms, in the streets of its towns and cities. And that threatens a grim fate for many thousands more Syrians both before, and after Assad goes, with potential reverberations all across the “arc of instability” that runs from Lebanon to Afghanistan.

Tony Karon is a senior editor at TIME, where he has covered international conflicts in the Middle East, Asia, and the Balkans since 1997. A native of South Africa, he now resides with his family in Brooklyn, New York.